Rice blast control agents

ABSTRACT

Disclosed is a compound of formula (1) or an acid addition salt thereof which has excellent rice blast control effect:  
                 
 
     wherein  
     R represents a hydrogen atom, —COR 1 , —COOR 1 , in which R 1  represents alkyl having 1 to 4 carbon atoms, —COCH 2 OCH 3 , or —COCH 2 OCOCH 3 .

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a controlling agent for riceblast.

[0003] 2. Background Art

[0004] Up to now, a large number of active compounds having controleffect against various plant diseases have been found, and variouscontrolling agents for plant diseases, comprising them as activeingredients have been developed. For example, from the viewpoint ofappearance of resistant strains, however, there is room for improvementin control effect of the controlling agents.

[0005] Blast may be mentioned as one of plant diseases, and is inducedby infection of fungi of the genus Pyricularia which are a kind of moldfungi and belong to deuteromycotina. In particular, an outbreak of riceblast sometimes takes place in abnormal weather such as low temperatureor much rain in the summer period, and, thus, rice blast is one of themost serious diseases of rice.

[0006] For this reason, the development of controlling agents havingexcellent control effect against rice blast has been desired.

[0007] International Publication WO 98/55460 discloses 4-quinolinolderivatives and fungicides for agricultural and horticulturalapplications, comprising these derivatives as active ingredients. Inthis publication, however, there is no description on usefulness of2,3-dimethyl-6-t-butyl-8-fluoro-4-quinolinol derivatives.

SUMMARY OF THE INVENTION

[0008] The present inventors have now found that, among 4-quinolinolderivatives, those having t-butyl (tertiary butyl) at the 6-position andfluorine at the 8-position, that is,2,3-dimethyl-6-t-butyl-8-fluoro-4-quinolinol derivatives, havesignificantly high control effect against rice blast. This controleffect is significantly superior to that attained by other 4-quinolinolderivatives disclosed, for example, in International Publication WO98/55460. The present invention has been made based on such finding.

[0009] Accordingly, it is an object of the present invention to providea compound and a controlling agent which have excellent control effectagainst rice blast.

[0010] According to one aspect of the present invention, there isprovided a compound of formula (1) or an acid addition salt thereof:

[0011] wherein

[0012] R represents a hydrogen atom, —COR¹, —COOR¹, in which R¹represents alkyl having 1 to 4 carbon atoms, —COCH₂OCH₃, or—COCH₂OCOCH₃.

[0013] According to another aspect of the present invention, there isprovided a controlling agent for rice blast, comprising as activeingredients at least one compound selected from the group consisting ofthe compounds of formula (1) or acid addition salts thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Compounds of Formula (1)

[0015] The present invention relates to the compounds of formula (1)(2,3-dimethyl-6-t-butyl-8-fluoro-4-quinolinol derivatives) or acidaddition salts thereof. The compounds of formula (1) or acid additionsalts thereof have excellent control effect against rice blast(Pyricularia oryzae) and can be advantageously used as controllingagents for rice blast.

[0016] In the compounds of formula (1), R represents a hydrogen atom,—COR¹, —COOR¹, —COCH₂OCH₃, or —COCH₂OCOCH₃, wherein R¹ represents alkylhaving 1 to 4 carbon atoms, for example, methyl, ethyl, propyl, orbutyl.

[0017] In formula (1), when R represents a hydrogen atom, the compoundsof formula (1) may take a structure of formula (2) which is a tautomerof the compounds of formula (1). It would be apparent to a person havingordinary skill in the art that the compounds of formula (1) embrace thecompounds of formula (2).

[0018] In the present invention, the term “acid addition salt” refers tosalts, which are generally usable in the fields of agriculture andhorticulture, for example, hydrochlorides, nitrates, sulfates,phosphates, and acetates.

[0019] It should be noted that the compounds of formula (1) may take theform of hydrates or solvates. In the present invention, such hydratesand solvates are also embraced in the compounds of formula (1).

[0020] Specific examples of compounds of formula (1) include:

[0021] 2,3-dimethyl-6-t-butyl-8-fluoro-4-hydroxyquinoline;

[0022] 2,3-dimethyl-6-t-butyl-8-fluoro-4-acetylquinoline;

[0023] 2,3-dimethyl-6-t-butyl-8-fluoro-4-propionyl-quinoline;

[0024] 2,3-dimethyl-6-t-butyl-8-fluoro-4-butyrylquinoline;

[0025] 2,3-dimethyl-6-t-butyl-8-fluoro-4-valerylquinoline;

[0026] 2,3-dimethyl-6-t-butyl-8-fluoro-4-methoxycarbonyl-quinoline;

[0027] 2,3-dimethyl-6-t-butyl-8-fluoro-4-ethoxycarbonyl-quinoline;

[0028] 2,3-dimethyl-6-t-butyl-8-fluoro-4-n-propoxy-carbonylquinoline;

[0029] 2,3-dimethyl-6-t-butyl-8-fluoro-4-n-butoxycarbonyl-quinoline;

[0030] 2,3-dimethyl-6-t-butyl-8-fluoro-4-methoxyacetyl-quinoline; and

[0031] 2,3-dimethyl-6-t-butyl-8-fluoro-4-acetoxyacetyl-quinoline.

[0032] Production Process of Compounds of Formula (1)

[0033] The compounds of formula (1) according to the present inventionmay be synthesized by any appropriate process regarding the formation ofa bond or the introduction of a substituent.

[0034] For example, a compound of formula (1) can be produced from4-t-butyl-2-fluoroaniline, which can be synthesized by a conventionalmethod, according to the following scheme.

[0035] wherein

[0036] R represents a hydrogen atom, —COR¹, —COOR¹, in which R¹represents alkyl having 1 to 4 carbon atoms, —COCH₂OCH₃, or—COCH₂OCOCH₃, and R² represents R¹, —OR¹, —CH₂OCH₃, or —CH₂OCOCH₃.

[0037] According to this scheme, a compound of formula (2) is firstprovided (step (a)), and the compound of formula (2) is then reactedwith the compound of formula (3) or (4) in the presence or absence of abase (step (b)) to give the compound of formula (1).

[0038] The above scheme will be described in more detail.

[0039] Step (a)

[0040] At the outset, a compound of formula (2) is prepared from4-t-butyl-2-fluoroaniline and ethyl 2-methyl-acetoacetate, for example,according to J. Am. Chem. Soc. 70, 2402 (1948), Tetrahedron Lett. 27,5323 (1986). The compound of formula (2) corresponds to the compound offormula (1) wherein R represents a hydrogen atom.4-t-Butyl-2-fluoroaniline used herein may be prepared by a conventionalmethod described, for example, in Chem. Abs. 42, 2239 or J. Chem. Soc.,Chem. Commun., 1992, 595.

[0041] Step (b)

[0042] Next, when a compound of formula (1), wherein R represents agroup other than a hydrogen atom, is desired, this compound can beproduced by reacting the compound of formula (2) with the compound offormula (3) or (4) in the presence or absence of a base.

[0043] Bases usable herein include, for example, organic amines, such astriethylamine and pyridine, and inorganic bases, such as sodiumcarbonate, potassium carbonate, and sodium hydride. The compound offormula (3) or (4) is preferably used in an amount of 1 to 50equivalents, more preferably 1 to 10 equivalents, based on the compoundof formula (2). The reaction in step (b) may be carried out in theabsence of a solvent or in the presence of an organic solvent inert tothe reaction, for example, dimethylformamide or tetrahydrofuran, forexample, in the temperature range of 0 to 140° C.

[0044] Controlling Agent for Rice Blast

[0045] The controlling agent for rice blast according to the presentinvention comprises as an active ingredient at least one compoundselected from the group consisting of the compounds of formula (1) oracid addition salts thereof.

[0046] The expression “comprising as an active ingredient” as usedherein means that a carrier according to the formulation may of coursebe incorporated and, in addition, other chemical agents usable incombination with the compound of the present invention may beincorporated.

[0047] Accordingly, when the compound of formula (1) is used as acontrolling agent for rice blast, the compound of formula (1) as suchmay be used. In general, however, the compound of formula (1) may bemixed, for example, with suitable solid carriers, liquid carriers,gaseous carriers, surfactants, dispersants and/or other adjuvants forformulations, to prepare any suitable formulation, such as emulsifiableconcentrates, liquid formulations, wettable powder, dust formulation,granules, oil solutions, aerosols, or flowables.

[0048] Solid carriers usable herein include, for example, talc,bentonite, clay, kaolin, diatomaceous earth, vermiculite, white carbon,and calcium carbonate.

[0049] Examples of liquid carriers include: alcohols, such as methanol,n-hexanol, and ethylene glycol; ketones, such as acetone, methyl ethylketone, and cyclohexanone; aliphatic hydrocarbons, such as n-hexane,kerosine, and kerosene; aromatic hydrocarbons, such as toluene, xylene,and methylnaphthalene; ethers, such as diethyl ether, dioxane, andtetrahydrofuran; esters, such as ethyl acetate; nitrites, such asacetonitrile and isobutyronitrile; acid amides, such asdimethylformamide and dimethylacetamide; vegetable oils, such as soybean oil and cotton seed oil; dimethylsulfoxide; and water.

[0050] Gaseous carriers include, for example, LPG, air, nitrogen, carbondioxide, and dimethyl ether.

[0051] Surfactants or dispersants usable, for example, for emulsifying,dispersing, or wetting the compound of formula (1) include, for example,alkylsulfonic esters, alkylsulfonic acid salts, alkylarylsulfonic acidsalts, polyoxyalkylene alkyl ethers, polyoxyalkylene alkylaryl ethers,polyhydric alcohol esters, and lignin sulfonic acid salts.

[0052] Adjuvants usable for improving the properties of formulationsinclude, for example, carboxymethylcellulose, gum arabic, polyethyleneglycol, and calcium stearate.

[0053] At least two members may be selected from the above group ofcarriers, group of surfactants, group of dispersants, and group ofadjuvants (the selected members may belong to the same group ordifferent groups) and used in combination.

[0054] The content of the compound of formula (1) or acid addition saltthereof in the controlling agent for rice blast may be properly variedby taking into consideration formulations, application methods andapplication environment of the controlling agent and other conditions.The content of the compound of formula (1) is generally 1 to 75% byweight, preferably 5 to 30% by weight, when the controlling agent is anemulsifiable concentrate; generally 0.3 to 25% by weight, preferably 1to 3% by weight, when the controlling agent is dust; generally 1 to 90%by weight, preferably 5 to 50% by weight, when the controlling agent iswettable powder; and generally 0.5 to 50% by weight, preferably 2 to 30%by weight, when the controlling agent is granules.

[0055] The controlling agent for rice blast according to the presentinvention is generally used as such or after dilution.

[0056] Methods of application of the controlling agent for rice blastaccording to the present invention include, for example, application torice plant per se (application to stems and leaves), application tonursery boxes, application to soil (admixing with soil or sidedressing(i.e. what is called “sokujou” in Japanese), application tofield water (application to water surface or application to regularpaddy field), and application to seeds (seed treatment).

[0057] According to a further aspect of the present invention, there isprovided a method for controlling rice blast, comprising the step ofapplying the compound of formula (1) or acid addition salt thereof to arice plant per se, soil, or field water.

[0058] The controlling agent for rice blast according to the presentinvention may be applied in an amount which is properly determined bytaking into consideration, for example, application environment andstate of growth and development of rice plant. For example, however,when the controlling agent is applied to soil or field water for thegrowth and development of rice plants, the amount of the controllingagent in terms of the amount of the active ingredient is preferably 9 to500 g, more preferably 30 to 300 g, per 10 ares.

[0059] Further, the controlling agent for rice blast according to thepresent invention may be used as a mixture, for example, with otherfungicides, bactericides, insecticides, miticides, herbicides, plantgrowth-regulating agents, or fertilizers.

EXAMPLES

[0060] The following examples further illustrate the present invention,but are not intended to limit it.

Production Examples

[0061] Compounds 1 to 11 according to the present invention wereproduced as follows. For comparison, compounds 12 to 14 were produced inthe same manner as used in the production of the compounds 1 to 11.

[0062] Production of 4-t-butyl-2-fluoroaniline

[0063] SELECTFLUOR (manufactured by Aldrich Chemical Company Inc.)(1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2,2,2]octanebistetrafluoroborate) (15 g) was added to acetonitrile (200ml), and mixture was heated at 70° C. for 30 min to dissolve SELECTFLUORin acetonitrile. The reaction solution thus obtained was cooled to 60°C., and 4-t-butyl-acetanilide (5.7 g) was added to the cooled reactionsolution. The mixture was stirred at 100° C. for one hr, and thereaction solution was then allowed to stand for cooling. The cooledreaction solution was then added to water (200 ml), followed byextraction with ethyl acetate (100 ml, twice). The ethyl acetate layerwas washed with saturated brine and was dried over anhydrous sodiumsulfate, and the solvent was then removed under the reduced pressure.The crude product thus obtained was purified by chromatography on silicagel (Wako Gel C-200 manufactured by Wako Pure Chemical Industries, Ltd.,elution solvent: n-hexane-ethyl acetate (10:1)) to give4-t-butyl-2-fluoro-acetanilide (3.06 g). This4-t-butyl-2-fluoro-acetanilide (3.67 g) was added to a mixed solutioncomposed of ethanol (30 ml) and concentrated hydrochloric acid (15 ml),and the mixture was stirred at 95° C. for 2 hr. The reaction solutionwas allowed to stand for cooling, and the cooled reaction solution wasthen poured into water, followed by neutralization with a saturatedaqueous sodium hydrogencarbonate solution and extraction with ethylacetate. The ethyl acetate layer was washed with a saturated aqueoussodium hydrogencarbonate solution and saturated brine, and was driedover anhydrous sodium sulfate. The solvent was then removed under thereduced pressure to give 4-t-butyl-2-fluoroaniline (3.49 g). ¹H-NMR dataon this compound in deutro-chloroform were as shown below.

[0064] δ (ppm): 7.01 (1H, dd), 6.95 (1H, dd), 6.73 (1H, m), 1.28 (9H,s)

Compound 1: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-hydroxyguinoline

[0065] 4-t-Butyl-2-fluoroaniline (4.79 g) prepared according to theabove process and ethyl 2-methyl-acetoacetate (4.96 g) were refluxed intoluene (60 ml) in the presence of trifluoroboron etherate (0.3 ml) for3 hr to obtain a reaction solution. The reaction solution thus obtainedwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was dried over anhydrous sodium sulfate. Thesolvent was then removed under the reduced pressure. The reactionproduct was refluxed in diphenyl ether (80 ml) for one hr and wasallowed to stand for cooling. The precipitated product was thencollected by filtration under the reduced pressure to give2,3-dimethyl-6-t-butyl-8-fluoro-4-hydroxyquinoline (compound 1, 1.66 g).¹H-NMR data on this compound in deutro-DMSO (dimethyl sulfoxide) were asshown below.

[0066] δ (ppm) : 11.27 (1H, br.s), 7.83 (1H, s), 7.59 (1H, br.d), 2.41(3H, s), 1.96 (3H, s), 1.31 (9H, s)

Compound 2: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-acetyl-quinoline

[0067] The compound 1 (50 mg) was stirred in acetic anhydride (3 ml) at120° C. for 3 hr to obtain a reaction solution. Acetic anhydride wasremoved from the reaction solution under the reduced pressure. Theresidue was dissolved in ethyl acetate. The solution was washed with asaturated aqueous sodium hydrogencarbonate solution and saturated brineand was then dried over anhydrous sodium sulfate, and the solvent wasthen removed under the reduced pressure. The crude product was purifiedby chromatography on silica gel (Wako Gel C-200, elution solvent:n-hexane-ethyl acetate (5:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-acetylquinoline (compound 2, 35.7 mg).¹H-NMR data on this compound in deutro-chloroform were as shown below.

[0068] δ (ppm): 7.43 (1H, dd), 7.37 (1H, d), 2.78 (3H, s), 2.51 (3H, s),2.26 (3H, s), 1.38 (9H, s)

Compound 3: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-propionylquinoline

[0069] In tetrahydrofuran (3 ml) was suspended 60% sodium hydride (20mg). The compound 1 (124 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, propionylchloride (200 μl) was added thereto, and the mixture was stirred for 3hr. The reaction solution thus obtained was poured into ice water, andthe mixture was extracted with ethyl acetate. The ethyl acetate layerwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was then dried over anhydrous sodium sulfate.The solvent was then removed under the reduced pressure. The crudeproduct was purified by chromatography on silica gel (Wako Gel C-200,elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-propionylquinoline (compound 3, 21mg). ¹H-NMR data on this compound in deutro-chloroform were as shownbelow.

[0070] δ (ppm): 7.42 (1H, dd), 7.36 (1H, d), 2.81 (2H, 35 q), 2.75 (3H,s), 2.25 (3H, s), 1.43 (3H, t), 1.37 (9H, S)

Compound 4: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-butyryl-quinoline

[0071] In tetrahydrofuran (3 ml) was suspended 60% sodium hydride (20mg). The compound 1 (124 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, butyrylchloride (200 μl) was added thereto, and the mixture was stirred for 3hr. The reaction solution thus obtained was poured into ice water, andthe mixture was extracted with ethyl acetate. The ethyl acetate layerwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was then dried over anhydrous sodium sulfate.The solvent was then removed under the reduced pressure. The crudeproduct was purified by chromatography on silica gel (Wako Gel C-200,elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-butyrylquinoline (compound 4, 64 mg).¹H-NMR data on this compound in deutro-chloroform were as shown below.

[0072] δ (ppm): 7.43 (1H, dd), 7.37 (1H, d), 2.76 (2H, t), 2.75 (3H, s),2.25 (3H, s), 1.94 (2H, m), 1.37 (9H, s), 1.15 (3H, t)

Compound 5: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-valeryl-quinoline

[0073] In tetrahydrofuran (3 ml) was suspended 60% sodium hydride (20mg). The compound 1 (124 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, valerylchloride (200 μl) was added thereto, and the mixture was stirred for 3hr. The reaction solution thus obtained was poured into ice water, andthe mixture was extracted with ethyl acetate. The ethyl acetate layerwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was then dried over anhydrous sodium sulfate.The solvent was then removed under the reduced pressure. The crudeproduct was purified by chromatography on silica gel (Wako Gel C-200,elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-valerylquinoline (compound 5, 120 mg).¹H-NMR data on this compound in deutro-chloroform were as shown below.

[0074] δ (ppm): 7.42 (1H, dd), 7.37 (1H, d), 2.78 (2H, t), 2.75 (3H, s),2.25 (3H, s), 1.89 (2H, m), 1.56 (2H, m), 1.37 (9H, s), 1.03 (3H, t)

Compound 6: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-methoxy-carbonylquinoline

[0075] In tetrahydrofuran (3 ml) was suspended 60% sodium hydride (20mg). The compound 1 (124 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, methylchloroformate (200 μl) was added thereto, and the mixture was stirredfor 3 hr. The reaction solution thus obtained was poured into ice water,and the mixture was extracted with ethyl acetate. The ethyl acetatelayer was washed with a saturated aqueous sodium hydrogencarbonatesolution and saturated brine and was then dried over anhydrous sodiumsulfate. The solvent was then removed under the reduced pressure. Thecrude product was purified by chromatography on silica gel (Wako GelC-200, elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-methoxycarbonyl-quinoline (compound 6,100 mg). ¹H-NMR data on this compound in deutro-chloroform were as shownbelow.

[0076] δ (ppm): 7.45 (1H, br.s), 7.43 (1H, dd), 4.00 (3H, s), 2.76 (3H,s), 2.31 (3H, s), 1.38 (9H, s)

Compound 7: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-ethoxy-carbonylquinoline

[0077] In tetrahydrofuran (10 ml) was suspended 60% sodium hydride (60mg). The compound 1 (200 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, ethylchloroformate (200 μl) was added thereto, and the mixture was stirredfor 3 hr. The reaction solution thus obtained was poured into ice water,and the mixture was extracted with ethyl acetate. The ethyl acetatelayer was washed with a saturated aqueous sodium hydrogencarbonatesolution and saturated brine and was then dried over anhydrous sodiumsulfate. The solvent was then removed under the reduced pressure. Thecrude product was purified by chromatography on silica gel (Wako GelC-200, elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-ethoxycarbonyl-quinoline (compound 7,220 mg).

[0078]¹H-NMR data on this compound in deutro-chloroform were as shownbelow.

[0079] δ (ppm): 7.45 (1H, br.s), 7.43 (1H, dd), 4.40 (2H, q), 2.32 (3H,s), 2.04 (3H, s), 1.44 (3H, t), 1.38 (9H, S)

Compound 8:2,3-Dimethyl-6-t-butyl-8-fluoro-4-n-propoxy-carbonylquinoline

[0080] In tetrahydrofuran (3 ml) was suspended 60% sodium hydride (20mg). The compound 1 (124 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, n-propylchloroformate (200 μl) was added thereto, and the mixture was stirredfor 3 hr. The reaction solution thus obtained was poured into ice water,and the mixture was extracted with ethyl acetate. The ethyl acetatelayer was washed with a saturated aqueous sodium hydrogencarbonatesolution and saturated brine and was then dried over anhydrous sodiumsulfate. The solvent was then removed under the reduced pressure. Thecrude product was purified by chromatography on silica gel (Wako GelC-200, elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-n-propoxycarbonyl-quinoline (compound8, 96 mg). ¹H-NMR data on this compound in deutro-chloroform were asshown below.

[0081] δ (ppm): 7.45 (1H, br.s), 7.43 (1H, dd), 4.35 (2H, t), 2.75 (3H,s), 2.31 (3H, s), 1.82 (2H, m), 1.38 (9H, s), 1.04 (3H, t)

Compound 9: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-n-butoxy-carbonylquinoline

[0082] In tetrahydrofuran (10 ml) was suspended 60% sodium hydride (60mg). The compound 1 (200 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, n-butylchloroformate (200 μl) was added thereto, and the mixture was stirredfor 3 hr. The reaction solution thus obtained was poured into ice water,and the mixture was extracted with ethyl acetate. The ethyl acetatelayer was washed with a saturated aqueous sodium hydrogencarbonatesolution and saturated brine and was then dried over anhydrous sodiumsulfate. The solvent was then removed under the reduced pressure. Thecrude product was purified by chromatography on silica gel (Wako GelC-200, elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-n-butoxycarbonyl-quinoline (compound9, 142 mg). ¹H-NMR data on this compound in deutro-chloroform were asshown below.

[0083] δ (ppm): 7.45 (1H, d), 7.43 (1H, dd), 4.35 (2H, t), 2.75 (3H, s),2.32 (3H, s), 1.77 (2H, m), 1.48 (2H, m), 1.38 (9H, s), 0.99 (3H, t)

Compound 10: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-methoxy-acetylquinoline

[0084] In tetrahydrofuran (10 ml) was suspended 60% sodium hydride (165mg). The compound 1 (680 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, methoxyacetylchloride (200 μl) was added thereto, and the mixture was stirred for 3hr. The reaction solution thus obtained was poured into ice water, andthe mixture was extracted with ethyl acetate. The ethyl acetate layerwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was then dried over anhydrous sodium sulfate.The solvent was then removed under the reduced pressure. The crudeproduct was purified by chromatography on silica gel (Wako Gel C-200,elution solvent: n-hexane-ethyl acetate (3:1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-methoxyacetylquinoline (compound 10,390 mg). ¹H-NMR data on this compound in deutro-chloroform were as shownbelow.

[0085] δ (ppm): 7.42 (1H, dd), 7.35 (1H, d), 4.51 (2H, s), 3.62 (3H, s),2.75 (3H, s), 2.26 (3H, s), 1.37 (9H, S)

Compound 11: 2,3-Dimethyl-6-t-butyl-8-fluoro-4-acetoxy-acetylquinoline

[0086] In tetrahydrofuran (10 ml) was suspended 60% sodium hydride (44mg). The compound 1 (200 mg) was added to the suspension under icecooling, and the mixture was stirred for 30 min. Further, acetoxyacetylchloride (100 μl) was added thereto, and the mixture was stirred for 3hr. The reaction solution thus obtained was poured into ice water, andthe mixture was extracted with ethyl acetate. The ethyl acetate layerwas washed with a saturated aqueous sodium hydrogencarbonate solutionand saturated brine and was then dried over anhydrous sodium sulfate.The solvent was then removed under the reduced pressure. The crudeproduct was purified by chromatography on silica gel (Wako Gel C-200,elution solvent: n-hexane-ethyl acetate (3 : 1)) to give2,3-dimethyl-6-t-butyl-8-fluoro-4-acetoxyacetylquinoline (compound 11,140 mg). ¹H-NMR data on this compound in deutro-chloroform were as shownbelow.

[0087] δ (ppm): 7.43 (1H, dd), 7.42 (1H, br.s), 5.02 (2H, s), 2.75 (3H,s), 2.27 (3H, s), 2.23 (3H, s), 1.40 (9H, s)

Compounds 12 to 14 (Comparative)

[0088] Compounds 12 to 14 having respective structures as shown in Table1 below were produced in the same manner as used in the production ofthe above compounds. These compounds 12 to 14 are comparative compoundsrelative to the present invention.

Production of Rice Blast Controlling Agents Production Example 1:Wettable powder

[0089] Intimate mixing was carried out according to the followingformulation, and the mixture was ground to produce wettable powder.Compound 2 25 wt % Clay 30 wt % Diatomaceous earth 35 wt % Calciumlignin sulfonate  3 wt % Polyoxyethylene alkylaryl ether  7 wt %

Production Example 2: Dust

[0090] Intimate mixing was carried out according to the followingformulation to produce dust. Compound 2  2 wt % Clay 60 wt % Talc 37 wt% Calcium stearate  1 wt %

Production Example 3: Emulsifiable Concentrate

[0091] Intimate mixing and dissolution were carried out according to thefollowing formulation to produce an emulsifiable concentrate. Compound 220 wt % N,N-Dimethylformamide 20 wt % Xylene 50 wt % Polyoxyethylenealkylaryl ether 10 wt %

Evaluation Test

[0092] Test 1: Rice Blast Infection Inhibition Test (Rice BlastPreventive Test)

[0093] Full fourth-leaf stage rice seedlings (variety: Jikkoku) raisedin each of plastic pots containing compost for about 15 days afterseeding were provided as a test plant.

[0094] The rice blast controlling agent according to the presentinvention was diluted with a 10% aqueous acetone solution (with2000-fold diluted Neoesterin® added thereto) to predeterminedconcentrations. Thus, test solution were prepared. Each of the testsolution thus prepared was applied in an amount of 10 ml per three potsby means of a spray gun to the test plant, followed by air drying.

[0095] Next, rice blast fungi, which have been previously cultured inpetri dish, were collected and were used to prepare a conidialsuspension (1 to 5×10⁶/ml). This conidial suspension was homogeneouslysprayed and inoculated into the pots. The pots were then allowed tostand in a moist chamber of 25° C. for 24 hr. Thereafter, the pots weretransferred to an environment controlled greenhouse kept at 20° C. atnight and at 25° C. in the daytime to induce the disease.

[0096] Seven days after the inoculation, the number of lesions which hadappeared in the fourth leaf were counted to obtain the results in thetreated plot and the results in the nontreated plot. For each case, theprotective value was calculated by the following equation.

[0097] Protective value=[1−(number of lesions in treated plot/number oflesions in nontreated plot)]×100

[0098] The results were as summarized in Table 1. TABLE 1

Com- Concentration, Protective pound No. R² R³ R⁴ ppm value 1 t-Bu F —H10 100 3 93 2 t-Bu F —COCH₃ 10 100 3 94 5 t-Bu F —CO(CH₂)₃CH₃ 10 99 3 846 t-Bu F —COOCH₃ 10 100 3 95 7 t-Bu F —COOCH₂CH₃ 10 100 3 95 8 t-Bu F—COO(CH₂)₂CH₃ 10 100 3 92 9 t-Bu F —COO(CH₂)₃CH₃ 10 99 3 90 10 t-Bu F—COCH₂OCH₃ 10 100 3 99 11 t-Bu F —COCH₂OCOCH₃ 10 100 3 94 12 (Com- H H—COCH₃ 200 <49 parative) 13 (Com- H F —COCH₃ 200 <49 parative) 14 (Com-t-Bu H —COCH₃ 20 98 parative) 5 70 3 <49

Test 2: Rice Blast Lesion Evolution Inhibition Test (Rice BlastTreatment Test)

[0099] Full fourth-leaf stage rice seedlings (variety: Jikkoku) raisedin each of plastic pots containing compost for about 15 days afterseeding were provided as a test plant.

[0100] Rice blast fungi, which have been previously cultured in petridish, were collected and were used to prepare a conidial suspension (1to 5×10⁶/ml). This conidial suspension was homogeneously sprayed andinoculated into the pots. The pots were then allowed to stand in a moistchamber of 25° C. for 24 hr. Thereafter, the pots were transferred to anenvironment controlled greenhouse kept at 20° C. at night and at 25° C.in the daytime to induce the disease.

[0101] After the elapse of 48 hr from the inoculation, the rice blastcontrolling agent according to the present invention was brought topredetermined concentrations to prepare test solution. Each of the testsolution was applied in an amount of 10 ml per three pots by means of aspray gun to the test plant, followed by air drying. Subsequently, thepots were again transferred to the environment controlled greenhouse toinduce the disease.

[0102] Seven days after the inoculation, the number of lesions which hadappeared in the fourth leaf were counted to obtain the results in thetreated plot and the results in the nontreated plot. For each case, theprotective value was calculated in the same manner as used in theinfection inhibition test.

[0103] The results were as shown in Table 2. TABLE 2

Com- Concentration, Protective pound No. R² R³ R⁴ ppm value 2 t-Bu F—COCH₃ 75 98 37.5 90 3 t-Bu F —COCH₂CH₃ 75 89 37.5 64 4 t-Bu F—CO(CH₂)₂CH₃ 75 94 37.5 66 5 t-Bu F —CO(CH₂)₃CH₃ 75 95 37.5 82 6 t-Bu F—COOCH₃ 75 92 37.5 68 7 t-Bu F —COOCH₂CH₃ 100 98 30 87 8 t-Bu F—COO(CH₂)₂CH₃ 100 98 30 84 9 t-Bu F —COO(CH₂)₃CH₃ 100 98 30 87 10 t-Bu F—COCH₂OCH₃ 100 100 30 90 11 t-Bu F —COCH₂OCOCH₃ 100 99 30 88 12 (Com- HH —COCH₃ 100 <49 parative) 13 (Com- H F —COCH₃ 100 <49 parative) 14(Com- t-Bu H —COCH₃ 100 81 parative) 50 <49

1. A compound of formula (1) or an acid addition salt thereof:

wherein R represents a hydrogen atom, —COR¹, —COOR¹, in which R¹represents alkyl having 1 to 4 carbon atoms, —COCH₂OCH₃, or—COCH₂OCOCH₃.
 2. The compound of formula (1) or acid addition saltthereof according to claim 1, for use in the control of rice blast.
 3. Acontrolling agent for rice blast, comprising as an active ingredient atleast one compound selected from the group consisting of the compoundsof formula (1) or acid addition salts thereof according to claim
 1. 4. Amethod for controlling rice blast, comprising the step of applying thecompound or acid addition salt thereof according to claim 1 to a riceplant per se, soil, or field water.
 5. Use of the compound or acidaddition salt thereof according to claim 1, for the production of acontrolling agent for rice blast.